The present invention relates to focusing the scanning light beam of a bar code reader. In particular, the present invention relates to automatically focusing the scanning light beam based upon the ability of the bar code reader to properly decode the electric signal produced by the reader's photodetector.
Typically, bar code reader manufacturers configure bar code readers to read bar codes positioned within a fixed range of distances from the reader. The fixed range of distances is normally set by the manufacturer based upon the bar code size and range of distances selected by the customer. The main problem with this type of system for setting reading distance ranges is the customers inability to utilize the reader for applications requiring a reading distance or code size outside of the range originally selected.
To avoid some of the problems caused by bar code readers having fixed reading distance ranges and fixed bar code size ranges, some modern bar code readers have also been manufactured with automatic focusing based upon distance sensors. These readers determine the actual distance between the reader and the code, and focus the scanning light beam based upon the distance. One drawback with this type of automatic focusing system is the additional cost of the distance detection circuitry and sensors. Another drawback with the system is that the system controls the distance between the focusing lens and the light beam source based upon the distance between the reader and the code rather than the decoding performance of the reader.
Accordingly, it would be desirable to provide a bar code reader with automatic focusing based upon the decoding performance of the reader or other parameter which optimizes the ability of the reader to provide optimal bar code reading for a wide range of reading distances.